1. Field
The present disclosure relates to projection optical systems and projection apparatuses.
2. Description of the Related Art
Conventionally, for example, Japanese Laid-Open Patent Publication No. 2005-257896 discloses a projection optical system of a six-unit configuration in which, in zooming, first and sixth lens units are fixed, and second to fifth lens units move.
Besides Japanese Laid-Open Patent Publication No. 2005-257896, there are Japanese Laid-Open Patent Publications Nos. 2003-015037, 2001-235679, 2004-138640, and 2011-100079 related to projection optical systems.